4 ROS2 - Services , Parameter, Actions

ROS2 Services

Open a new terminal and run:

ros2 run turtlesim turtlesim_node

Open another terminal and run:

ros2 run turtlesim turtle_teleop_key

Open another terminal and run:

ros2 service list

To see service and type together

ros2 service list -t

To see the request and response arguments of the /spawn service, run the command:

ros2 interface show turtlesim/srv/Spawn

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ROS service call

Now that you know what a service type is, how to find a service’s type, and how to find the structure of that type’s arguments, you can call a service using:

ros2 service call <service_name> <service_type> <arguments>

ros2 service call /clear std_srvs/srv/Empty

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ROS2 Param List

Open another terminal and run:

ros2 param list

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ROS2 Param Get

To display the type and current value of a parameter, use the command:
ros2 param get <node_name> <parameter_name>

ros2 param get /turtlesim background_g

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ROS2 Param Set

To change a parameter’s value at runtime, use the command:
ros2 param set <node_name> <parameter_name> <value>

ros2 param set /turtlesim background_r 150

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ROS2 Param Dump

To save your current configuration of /turtlesim’s parameters, enter the command:

ros2 param dump /turtlesim

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ROS2 Param Load

Open another terminal and run:

ros2 param load /turtlesim ./turtlesim.yaml

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Load Parameter File on Node Startup

To start the same node using your saved parameter values, use:
ros2 run <package_name> <executable_name> --ros-args --params-file <file_name>

ros2 run turtlesim turtlesim_node --ros-args --params-file ./turtlesim.yaml

ROS2 Action

Open a new terminal and run:

ros2 run turtlesim turtlesim_node

Open another terminal and run:

ros2 run turtlesim turtle_teleop_key

Open another terminal and run:

ros2 service list

ROS2 Node Info

To see the list of actions a node provides, /turtlesim in this case, open a new terminal and run the command:

ros2 node info /turtlesim

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open a new terminal and run the command:

ros2 node info /teleop_turtle

ROS2 Action List

Open another terminal and run:

ros2 action list

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Command to show action and node info together:

ros2 action list -t

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ROS2 Action Info

You can further introspect the /turtle1/rotate_absolute action with the command:

ros2 action info /turtle1/rotate_absolute

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ROS2 Interface Show

To show data type together:

ros2 interface show turtlesim/action/RotateAbsolute

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ROS2 Action send_goal

Now let’s send an action goal from the command line with the following syntax:
ros2 action send_goal <action_name> <action_type> <values><values> need to be in YAML format.

ros2 action send_goal /turtle1/rotate_absolute turtlesim/action/RotateAbsolute "{theta: 1.57}"

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To see the feedback of this goal, add --feedback to the last command you ran

ros2 action send_goal /turtle1/rotate_absolute turtlesim/action/RotateAbsolute "{theta: -1.57}" –feedback

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